SMALL HOLDINGS 115 



was again grown over the whole field, but the 

 crop which was grown on the clover land 

 obtained 30 lb. more nitrogen than that 

 which followed the barley grown alone, in 

 spite of the fact that the previous clover 

 crop has removed 114 lb. more nitrogen per 

 acre than the first barley crop. After the 

 removal of the clover and barley in the 

 second year analysis showed an excess of 

 nitrogen in the clover land to a depth of 

 9 in., much greater than that in the barley 

 land. Long before the discovery of the 

 medium which enabled clover and other 

 leguminous plants to obtain free nitrogen 

 from the atmosphere, opinions were expressed 

 by a number of scientific agriculturists, 

 including the late Dr Voelcker and the French 

 chemist, Ville, that the atmosphere was the 

 source from which they obtained their nitrogen, 

 although in what way there was no evidence 

 to show. In 1886, however, the German, 

 Hellriegel, discovered that when farm plants 

 such as the grasses were grown in sterile 

 sand, they practically grew in proportion 

 to the quantity of combined nitrogen supplied, 

 and that they died as soon as the supply in 

 the seed was exhausted. 



A similar result followed the attempt to 



